1. Field of the Invention
The present invention relates to apparatus and method for readily purging air from a new brake master cylinder assembly, thus filling the master cylinder with brake fluid. This is a step which is preliminary to installing a new master brake cylinder in a motor vehicle, which process requires that all air be purged from the fluid circuit.
2. Description of the Prior Art
When a new master cylinder is to be installed in a motor vehicle, it must be purged of air or other gasses, and filled with brake fluid. This operation is performed when the vehicle is first manufactured, and may also be required periodically during the service life of the vehicle should the original master cylinder fail. In either case, purging of air is required for successful operation under the pressure normally imparted to the system to operate the brakes.
Master cylinders have become more complicated over time. For example, redundant circuits have been incorporated therein which require an equal number of discharge orifices for connection of hoses conducting pressurized fluid to each wheel.
Individual owners and even seasoned mechanics will occasionally fail to purge the cylinder effectively, and may return the new or rebuilt master cylinder to the manufacturer as defective. A variety of methods and apparatus to accomplish successful purging have been proposed in the prior art.
U.S. Pat. No. 4,800,725, issued to Robert Kaulig et al. on Jan. 31, 1989, teaches that air may be forced from a master cylinder bore by plugging threaded orifices and forcing the air into the fluid reservoir. However, the concept of filling the cylinder bore with stored brake fluid by relying upon a return stroke powered by a master cylinder return spring is not shown or suggested.
Plugging a threaded orifice with a screw is shown in U.S. Pat. No. 4,979,367, issued to Dino Crescentini on Dec. 25, 1990. However, the screw forms a permanent part of the master cylinder, and is provided to enable a user to selectively seal one orifice while employing a nearby counterpart for connection to the brake circuit. The novel feature is that the master cylinder is formed having a plurality of threaded appertures for connection to the brake circuit. One orifice is selected for connection, and the others are unnecessary, and must be plugged to enable operative pressure to be developed. In this respect, this patent teaches away from the present invention.
U.S. Pat. Nos. 4,170,280, issued to Maurice L. Schwarz on Oct. 9, 1979, 4,236,549, issued to Donald F. Salzmann on Dec. 2, 1980, 4,497,176, issued to Frank D. Rubin et al. on Feb. 5, 1985, 4,865,171, issued to Ronald J. Miller et al. on Sep. 12, 1989, 5,310,252, issued to Howard C. Stewart, Jr. on May 10, 1994, and 5,381,662, issued to Richard M. Ethen et al. on Jan. 17, 1995, and U.K. Pat. Application No. 2,074,271, dated Oct. 28, 1981, all illustrate various aspects of bleeding master cylinders and hydraulic brake systems. These patents neither show nor suggest the novel apparatus and method.
None of the above inventions and patents, taken either singly or in combination, is seen to describe the instant invention as claimed.